1. Field of the Invention
The present invention relates to a recording apparatus, for example, of inkjet type.
2. Discussion of Related Art
As a kind of recording apparatus, there is known an inkjet type recording apparatus for performing a recording operation. During the recording operation, an inkjet head unit is caused to eject recording materials (ink droplets) toward a recording medium, while a carriage carrying the head unit is moved such that the head unit is moved relative to the recording medium with a predetermined spacing distance therebetween being maintained
As such an inkjet type recording apparatus, there is a recording apparatus in which a head driver unit mounted on the carriage is arranged to receive various data signals such as drive data signals (recording data signals) and drive waveform signals that are outputted from a main circuit disposed in a stationary main body of the apparatus. The inkjet head unit (herein after referred to as “recording head unit ”) is operated by the head driver unit, so as to eject the ink droplets through a plurality of nozzles formed in the head unit.
FIG. 4 shows a basic arrangement of the recording apparatus. The head driver unit has four drive circuits 100C, 100M, 100Y, 100Bk arranged to receive serially transmitted drive data signals DATA C_0˜C_2, M_0˜M_2, Y_0˜Y_2, Bk_0˜Bk_2 (corresponding to cyan, magenta, yellow and black inks, respectively) and drive waveform signal sets FIRE C_1˜C_6, FIRE M_1˜M_6, FIRE Y_1˜Y_6, FIRE Bk_1˜Bk_6. Each of the serially transmitted drive data signals DATA C_0˜C_2, M_0˜M_2, Y_0˜Y_2, Bk_0˜Bk_2 is converted by a corresponding one of shift registers (serial-parallel converter) 101C, 101M, 101Y, 101Bk, into parallel data signals corresponding to respective nozzles. The parallel data signals are latched by D flip-flops 102C, 102M, 102Y, 102Bk. From among each of the drive waveform signal sets FIRE C_1˜C_6, FIRE M_1˜M_6, FIRE Y_1˜Y_6, FIRE Bk_1˜Bk_6, one drive waveform signal is selected by a corresponding one of multiplexers 103C, 103M, 103Y, 103Bk, based on the corresponding data signal. The multiplexers 103C, 103M, 103Y, 103Bk outputs the selected drive waveform signals, which are then received by respective driver buffers 105C, 105M, 105Y, 105Bk. Each of the driver buffers 105C, 105M, 105Y, 105Bk generates a drive signal having a predetermined voltage and a waveform corresponding to that of the received drive waveform signal, and then supplies the generated drive signal to each of actuators which are activated for ink ejection through the respective nozzles.
In the above-described recording apparatus, for performing a recording operation with gradation control, a plurality of drive waveform signals having respective different drive waveforms have to be available for each of the recording materials (different color inks), so that each recording material can be ejected as an ink droplet that is variable in its size. This arrangement results in increase of the number of signal wires required for supplying the drive waveform signals to the drive circuits of the head driver unit.
The increase of the number of the signal wires is disadvantageous in view of cost and maintenance performance. Particularly, where a flexible flat cable is used for transmitting the signals from the main circuit disposed in the stationary main body to the head driver unit carried by the carriage, the flexible flat wire has a width inevitably increased by the increased number of the signal wires, thereby necessitating a complicated disposition of the flexible flat cable and even increasing a load exerted on the carriage moved relative to the stationary main body.
In view of the above-described problems, there have been made various attempts to reduce the number of the signal wires for transmitting the drive waveform signals from the main circuit to the head driver unit. For example, there was proposed an arrangement, as disclosed in JP-2000-158643A, in which waveform-related data (e.g., data representative of pulse width) required for generation of drive waveform signals are serially transmitted to each of drive-waveform-signal generator circuits disposed in the recording head unit prior to a recording operation, and the drive waveform signals are generated based on the waveform-related data by the drive-waveform-signal generator circuits upon initiation of the recording operation.
In the above-described proposed arrangement, the number of the signal wires for transmitting the drive waveform signals from the main circuit to the head driver unit can be made smaller than in the conventional arrangement. However, the plurality of drive-waveform-signal generator circuits as extra components are required for the generations of the respective different drive waveform signals, whereby the recording head unit is inevitably increased in weight.
Meanwhile, it might be possible to establish an arrangement in which a full-color recording operation is made by using cyan, yellow and magenta inks without using a black ink, since a mixture of the cyan, yellow and magenta inks can provide an ink whose color is close to black. Such an arrangement could reduce the number of the signal wires, owing to elimination of signal wires serving for the black ink. However, the monochrome recording made by the mixture of the cyan, yellow and magenta inks cannot provide an image as clear as that provided by the monochrome recording made by the black ink, and is disadvantageous also with respect to cost performance. That is, the arrangement does not satisfy a need for a clear recording at a low cost. Further, since there is a requirement of recording with the drive waveform signals having respective waveforms suitable for characteristics of the respective color inks, the reduction of the number of the signal wires cannot be realized by arranging the drive waveform signal to be common to the respective color inks.